Providing acknowledgement information by a wireless device

ABSTRACT

In general, to provide acknowledgment information by a first wireless device, the first wireless device sends repeated instances of acknowledgment information in respective first and second frame structures, in response to receipt of first information from a second wireless device. In addition, the first wireless device also sends further acknowledgment information in the second frame structure that is responsive to second information received from the second wireless device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Submission Under 35 U.S.C. §371 for U.S. NationalStage Patent Application of International Application Number:PCT/US2009/063264, filed Nov. 4, 2009, entitled “PROVIDINGACKNOWLEDGEMENT INFORMATION BY A WIRELESS DEVICE,” which claims priorityto U.S. Provisional Application Ser. No: 61/111,126, filed Nov. 4, 2008,the entirety of both which are incorporated herein by reference.

BACKGROUND

Various wireless access technologies have been proposed or implementedto enable mobile stations to perform communications with other mobilestations or with wired terminals coupled to wired networks. Examples ofwireless access technologies include GSM (Global System for Mobilecommunications) and UMTS (Universal Mobile Telecommunications System)technologies, defined by the Third Generation Partnership Project(3GPP); and CDMA 2000 (Code Division Multiple Access 2000) technologies,defined by 3GPP2.

As part of the continuing evolution of wireless access technologies toimprove spectral efficiency, to improve services, to lower costs, and soforth, new standards have been proposed. One such new standard is theLong Term Evolution (LTE) (also referred to as the Evolved UniversalTerrestrial Radio Access (EUTRA) standard) from 3GPP, which seeks toenhance the UMTS technology.

In a wireless communications network, information is communicatedwirelessly between mobile stations and base stations. In response toinformation received in the downlink (from base station to a mobilestation), the mobile station can send acknowledgment information toeither provide a positive acknowledge (ACK) of successful receipt of thedata, or negative acknowledgment (NAK) to indicate that the data was notsuccessfully received. To improve reliability, a recent development ofLTE proposed use of ACK/NAK repetition, in which a mobile stationrepeats the sending of an ACK or NAK in response to downlink informationfrom the base station, to improve the likelihood that the base stationreceives the ACK or NAK. This may be particularly useful when the mobilestation is in a region of a cell or cell sector that has relatively poorwireless conditions, such as at the edge of the cell or cell sector, orin another location associated with obstructions that may result inreduced signal strength or increased noise.

An issue associated with repetition of ACK/NAK is that in response toconsecutively received pieces of downlink information, theacknowledgment information for such consecutively received pieces ofinformation may collide, which may cause the base station to notreliably receive the acknowledgment information associated with theconsecutively transmitted pieces of downlink information.

SUMMARY

In general, according to a preferred embodiment, a method of providingacknowledgment information by a first wireless device comprises thefirst wireless device sending repeated instances of acknowledgmentinformation in respective first and second frame structures, in responseto receipt of first information from a second wireless device. Inaddition, the first wireless device also sends further acknowledgmentinformation in the second frame structure that is responsive to secondinformation received from the second wireless device.

Other or alternative features will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are described with respect to thefollowing figures:

FIG. 1 is a block diagram of an example arrangement that includes awireless communications network that incorporates some preferredembodiments of the invention;

FIGS. 2 and 3 illustrate the sending of downlink data and responsiverepeated instances of acknowledgment information in accordance with somepreferred embodiments; and

FIG. 4 is a flow diagram of a process of sending acknowledgmentinformation, according to an embodiment.

DETAILED DESCRIPTION

In accordance with some preferred embodiments, a technique or mechanismis provided to allow for transmission of repeated instances ofacknowledgment information while avoiding the issue of collisions inacknowledgment information sent in response to multiple pieces ofreceived information. In some embodiments, the acknowledgmentinformation is sent by a mobile station in the uplink (from the mobilestation to the base station) in response to receipt of downlink datafrom the base station. The acknowledgment information includes either apositive acknowledgment (ACK) to indicate successful receipt of thedata, or a negative acknowledgment (NAK) to indicate unsuccessfulreceipt of the data.

To improve reliability under certain conditions, the mobile station canbe configured to perform ACK/NAK repetition, in which multiple instancesof the ACK/NAK information is sent in response to receipt of aparticular piece of downlink data. In some implementations, the numberof ACK/NAK repetitions configured in the mobile station can be two. Inother implementations, the mobile station can be configured to sendthree or four or more instances of the ACK/NAK information (number ofACK/NAK repetitions is three or four or more). ACK/NAK repetition isuseful when the mobile station is located in a region of a cell or cellsector that is associated with unreliable wireless signaling. Forexample, the mobile station may be located at the edge of the cell orcell sector, or the mobile station may be located in a region withobstructions that reduce signal strength or increase noise.

An issue associated with performing ACK/NAK repetition is the likelihoodof collisions of ACK/NAK information when the mobile station sendsrespective repeated ACK/NAKs in response to consecutively receivedpieces of downlink data. In accordance with some embodiments, toeliminate or reduce the likelihood of collisions of ACK/NAK information,the repeated instance of an ACK/NAK may be communicated in a format thatallows for multiple ACK/NAKs (that are responsive to different pieces ofdownlink data) to be transmitted together. Thus, this predefined formatallows for the repeated ACK/NAK responsive to a first piece of data tobe sent by the mobile station together with the first ACK/NAK responsiveto a second piece of downlink data.

In some embodiments, the wireless communications network is according tothe Long Term Evolution (LTE) standard from 3GPP (Third GenerationPartnership Project), which is an enhancement of the UMTS (UniversalMobile Telecommunications System) wireless technology. The LTE standardis also referred to as the EUTRA (Evolved Universal Terrestrial RadioAccess) standard. Reference to an LTE (or EUTRA) wireless communicationsnetwork refers to the wireless communications network that conforms tothe requirements of the LTE (or EUTRA) standard developed by 3GPP, asthat standard currently exists or as the standard evolves over time.Note that LTE (or EUTRA) can refer to the current LTE (or EUTRA)standard, or to modifications of the LTE (or EUTRA) standard that aremade over time. It is expected that in the future a standard that hasevolved from LTE (or EUTRA) may be referred to by another name. It iscontemplated that the term “LTE” or “EUTRA” as used herein is intendedto cover such future standards as well. In alternative embodiments,wireless communications networks according to other standards can beemployed.

Although reference has been made to transmitting repeated uplinkACK/NAKs in response to downlink data, it is noted that other preferredembodiments of the invention can be applied to scenarios in which a basestation transmits a downlink ACK/NAKs in response to uplink data fromthe mobile station. Moreover, although reference is made to sendingACK/NAK in response to received data, it is noted that ACK/NAK can alsobe sent in response to control signaling.

FIG. 1 shows an example wireless network in which some embodiments ofthe invention can be provided. The wireless network includes a basestation 100 that includes an antenna array or other antenna assembly 102for sending wireless signals into a cell sector 108. A cell sector isone section of a cell of a cellular network. In alternativeimplementations, element 108 can represent an entire cell. Moregenerally, a “cell segment” refers to either a cell or a cell sector.

Although just one base station is depicted in FIG. 1, it is noted that awireless network would typically include multiple base stations. In someembodiments, the wireless network is an LTE wireless network.

In an LTE wireless network, the base station 100 is an enhanced node B(“eNode B”), which includes a base transceiver station that includes theantenna array 102. The base station 100 may also include a radio networkcontroller that cooperates with the enhanced node B. The radio networkcontroller and/or enhanced node B can perform one or more of thefollowing tasks: radio resource management, mobility management formanaging mobility of mobile stations, routing of traffic, and so forth.Note that one radio network controller can access multiple eNode Bs, oralternatively, an eNode B can be accessed by more than one radio accesscontroller.

More generally, the term “base station” can refer to a cellular networkbase station, an access point used in any type of wireless network, orany type of wireless transmitter to communicate with mobile stations.

As depicted in FIG. 1, the base station 100 includes one or more centralprocessing units (CPUs) 122, which is (are) connected to storage 124.Moreover, the base station 100 includes software 126 that is executableon the CPU(s) 122 to perform tasks of the base station 100.

The mobile station 110 of FIG. 1 also includes one or more CPUs 130 thatare connected to storage 132. The mobile station 110 also includessoftware 134 that is executable on the CPU(s) 130 to perform tasks ofthe mobile station 110. In addition, the mobile station 110 includes aninterface 131 to communicate wirelessly with the base station 100.

The base station 100 is connected to a serving and/or packet datanetwork (PDN) gateway 112, which terminates the user plane interfacetoward the enhanced node B and assumes the responsibility for packetrouting and transfer towards an external network 114, which can be apacket data network such as the Internet or other types of network.

The arrangement depicted in FIG. 1 is provided for purposes of example.In other implementations, other wireless network arrangements are used.

In accordance with some embodiments, downlink data in an LTE wirelesscommunications network is transmitted in PDSCH (physical downlink sharedchannel) subframes. The PDSCH is a traffic channel. In otherimplementations, the downlink data can be transmitted in other downlinktraffic channels. An LTE subframe is a portion of an LTE frame. An LTEframe has a predefined overall time length that is divided into apredefined number of time slots. An LTE frame is made up of multiplesubframes, where an LTE subframe can include some predefined number ofthe slots (e.g., two slots) of the LTE frame.

In response to receiving downlink data in a PDSCH subframe, the mobilestation transmits acknowledgment information (ACK/NAK) to indicatesuccessful or unsuccessful receipt of the downlink data in the PDSCHsubframe. In some embodiments, the ACK/NAK is sent by the mobile stationin the uplink direction in a PUCCH (physical uplink control channel)subframe. More generally, the repeated instances of ACK/NAK are sent inconsecutive frame structures, where a “frame structure” can include asubframe or some other frame structure.

As noted above, ACK/NAK repetition can be enabled for at least onemobile station that the base station 100 is communicating with. If themobile station is configured to perform ACK/NAK repetition by sendingtwo repeated instances of the ACK/NAK, then the mobile station willrespond to a downlink PDSCH subframe by sending two repeated instancesof ACK/NAK in consecutive PUCCH subframes. For example, as shown in FIG.2, in response to downlink data_1 received in PDSCH subframe n, a mobilestation configured to perform ACK/NAK repetition will send two instancesof ACK/NAK (each instance represented as ACK/NAK_1) in consecutive PUCCHsubframes n+4 and n+5.

FIG. 2 also indicates that another piece of downlink data (data_2) isscheduled to be transmitted to the same mobile station in the nextconsecutive PDSCH subframe (n+1). Since the mobile station is configuredto perform ACK/NAK repetition, the mobile station will send two repeatedinstances of ACK/NAK_2 in consecutive PUCCH subframes (n30 5, n+6).

Note that in this example, one instance of ACK/NAK_1 and one instance ofACK/NAK_2 are scheduled to be transmitted in the same PUCCH subframe(n+5). If not properly handled, ACK/NAK_1 will collide with ACK/NAK_2 inPUCCH subframe n+5.

To address this issue, in accordance with some embodiments, ACK/NAK_1and ACK/NAK_2 are transmitted together in PUCCH subframe n+5 using apredefined format that allows for communication of multiple differentpieces of ACK/NAK information. In some embodiments, an ACK/NAK iscommunicated as a single bit, where the bit having a first value (e.g.,“1”) represents ACK, and the bit having a second value (e.g., “0”)represents NAK. In such embodiments, sending two pieces of ACK/NAKinformation refers to sending two information bits in the PUCCH subframe(e.g., ACK/NAK_1 is sent in a first bit, while ACK/NAK_2 is sent in asecond bit).

In one example implementation, the predefined format that allows fortransmission of multiple different ACK/NAK bits in the same PUCCHsubframe is referred to as format 1b. Format 1b differs from a differentPUCCH format 1a, in which only a single ACK/NAK bit is allowed in thePUCCH subframe. In the example of FIG. 2, ACK/NAK_1 sent in PUCCHsubframe n+4 is according to format 1a, and ACK/NAK_2 in PUCCH subframen+6 is also according to format 1a. However, ACK/NAK_1 and ACK/NAK_2 inPUCCH subframe n+5 are sent together according to format 1b. In oneimplementation, the two ACK/NAK bits are transmitted together using QPSK(quadrature phase-shift keying) modulation.

The ability to use different formats for communicating acknowledgmentinformation allows for greater flexibility in performing ACK/NAKrepetition, while avoiding or reducing the likelihood of ACK/NAKcollisions.

FIG. 3 shows another example in which the ACK/NAK repetition is set at 3(in other words three instances of ACK/NAK is sent by the mobile stationin response to downlink data in a particular PDSCH subframe). When theACK/NAK repetition is set at 3, data for the same mobile station cannotbe sent in the downlink direction in more than two consecutive PDSCHsubframes. Data for the same mobile station can be sent in twoconsecutive PDSCH subframes, followed by an intermediate subframe periodthat does not contain downlink data for the mobile station, thenfollowed by another PDSCH subframe that contains data for the samemobile station. In the example of FIG. 3, data_1, data_2, and data_3 aresent in three different PDSCH subframes to the same mobile station. Data_1 is sent in PDSCH subframe n data_2 is sent in PDSCH subframe n+1, anddata_3 is sent in PDSCH subframe n+3, where intermediate subframe n+2(which does not contain downlink data for the mobile station) isprovided to separate the transmission of data_2 and data_3. Downlinkdata can be scheduled to the same mobile station every two consecutivePDSCH subframes. However, after the two consecutive subframes, aseparation subframe has to be provided before another PDSCH subframe canbe sent to the same mobile station.

As further shown in FIG. 3, ACK/NAK_1 for data_1 is sent as threerepeated instances in consecutive PUCCH subframes n+4, n+5, and n+6. Thethree repeated instances of ACK/NAK_2 (responsive to data_2) are sent inPUCCH subframes n+5, n+6, and n+7. Note that PUCCH in subframe n+5 andn+6 each contains both ACK/NAK_1 and ACK/NAK_2. No data for the mobilestation is sent in PDSCH subframe n+2, since doing so would require anACK/NAK in PUCCH subframe n+6 which already is sending two other ACK/NAKbits. Thus, a separation PDSCH subframe is provided between data_2 anddata_3, such that ACK/NAK_3 starts in PUCCH subframe n+7 rather thanPUCCH subframe n+6.

FIG. 4 is a flow diagram of a process according to an embodiment that isperformed at the mobile station 110, which is assumed to be configuredto perform ACK/NAK repetition. First downlink data is received (at 402)in a downlink channel subframe, such as a PDSCH subframe. Seconddownlink data is received (at 404) in another PDSCH subframe, which canbe consecutive to the PDSCH subframe containing the first downlink data.In response to the first and second downlink data, the mobile stationprepares (at 406) the repeated instances of acknowledgment informationresponsive to the first and second downlink data. It is assumed that themobile station is configured to send two repeated instances in responseto each piece of downlink data.

The mobile station sends (at 408) the two repeated instances ofacknowledgment information responsive to the first downlink data infirst and second consecutive uplink control channel (e.g., PUCCH)subframes. The first uplink control channel is at some offset from thedownlink subframe carrying the first downlink data. The mobile stationsends repeated instances of the acknowledgment information responsive tothe second downlink data in second and third consecutive uplink controlchannel subframes (at 410).

Although reference is made to the mobile station performing the processof FIG. 4, it is noted that the base station can also be configured toperform the process of FIG. 4, where the base station is to acknowledgereceipt of uplink information data (and/or signaling) from a mobilestation.

In an alternative embodiment, it is contemplated that the mobile stationcan use a scheduled PUSCH (physical uplink shared channel) to send arepeated instance of ACK/NAK. Thus, for example, referring back to FIG.2, if a PUSCH is scheduled to be sent in subframe n+5, then theACK/NAK_1 that was supposed to have been sent in PUCCH subframe n+5 caninstead be sent in PUSCH subframe n+5. The second repeated ACK/NAK_1instance can be multiplexed with data on the PUSCH, according to the LTEstandard.

As yet another alternative, if a PUSCH transmission was scheduled forsubframe n+5, this PUSCH transmission can be skipped to avoid collisionwith the ACK/NAK scheduled to be sent in PUCCH subframe n+5.

The ACK/NAK repetition of a given mobile station is configurable by thebase station. For example, the base station can send a parameter to themobile station to specify the number of repetitions (2, 3, 4, or more).The mobile station-specific ACK/NAK repetition parameter can beconfigured by using RRC (radio resource control) signaling or other typeof control signaling.

Instructions of software described above (including software 126 and 130of FIG. 1) are loaded for execution on a processor (such as one or moreCPUs 122 and 130 in FIG. 1). The processor includes microprocessors,microcontrollers, processor modules or subsystems (including one or moremicroprocessors or microcontrollers), or other control or computingdevices. As used here, a “processor” can refer to a single component orto plural components (e.g., one CPU or multiple CPUs).

Data and instructions (of the software) are stored in respective storagedevices, which are implemented as one or more computer-readable orcomputer- usable storage media. The storage media include differentforms of memory including semiconductor memory devices such as dynamicor static random access memories (DRAMs or SRAMs), erasable andprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read-only memories (EEPROMs) and flash memories; magneticdisks such as fixed, floppy and removable disks; other magnetic mediaincluding tape; and optical media such as compact disks (CDs) or digitalvideo disks (DVDs). Note that the instructions of the software discussedabove can be provided on one computer-readable or computer-usablestorage medium, or alternatively, can be provided on multiplecomputer-readable or computer-usable storage media distributed in alarge system having possibly plural nodes. Such computer-readable orcomputer-usable storage medium or media is (are) considered to be partof an article (or article of manufacture). An article or article ofmanufacture can refer to any manufactured single component or multiplecomponents.

In the foregoing description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details. While the invention has been disclosedwith respect to a limited number of embodiments, those skilled in theart will appreciate numerous modifications and variations therefrom. Itis intended that the appended claims cover such modifications andvariations as fall within the true spirit and scope of the invention.

What is claimed is:
 1. A method of providing acknowledgment informationby a first wireless device, comprising: in response to receipt of firstinformation from a second wireless device, preparing, by the firstwireless device, to send repeated instances of acknowledgmentinformation for the first information; sending, by the first wirelessdevice, a first of the repeated instances of the acknowledgmentinformation in a first Evolved Universal Terrestrial Radio Access(EUTRA) subframe, and a second of the repeated instances in a second,successive EUTRA subframe; and sending, by the first wireless device,further acknowledgment information in the second EUTRA subframe, whereinthe further acknowledgment information is responsive to secondinformation received from the second wireless device, wherein sendingthe second of the repeated instances of the acknowledgment informationcomprises using a first information bit of the second EUTRA subframe,and wherein sending the further acknowledgment information comprisesusing a second information bit of the second EUTRA subframe.
 2. Themethod of claim 1, wherein using the first and second bits comprisesusing first and second ACK/NAK bits.
 3. The method of claim 2, furthercomprising modulating the first and second 2 ACK/NAK bits in an uplinkcontrol channel subframe.
 4. The method of claim 2, wherein using thefirst and second ACKINAK bits comprises using the first and secondACK/NAK bits of uplink control information in a physical uplink controlchannel (PUCCH) subframe.
 5. The method of claim 1, wherein sending therepeated instances of the acknowledgment information in the respectivefirst and second EUTRA subframes comprises sending the repeatedinstances of the acknowledgment information in the respective first andsecond EUTRA subframes of a control channel, wherein the first instanceof the acknowledgment information is sent according to a first format ofthe control channel, and the second instance of the acknowledgmentinformation is sent according to a second, different format of thecontrol channel.
 6. The method of claim 5, wherein the control channelis a physical uplink control channel (PUCCH).
 7. The method of claim 1,further comprising receiving the first information in a physicaldownlink traffic channel.
 8. The method of claim 1, further comprising:receiving third information from the second wireless device; sending, bythe first wireless device, the first of repeated instances ofacknowledgment information for the third information in a third EUTRAsubframe, and a second of the repeated instances of the acknowledgmentinformation for the third information in a fourth EUTRA subframe,wherein the first instance of the acknowledgment information for thethird information is sent in a control channel, and the second instanceof the acknowledgment information for the third information is sent in atraffic channel.
 9. The method of claim 8, wherein the control channelis a physical uplink control channel (PUCCH), and the traffic channel isa physical uplink shared channel (PUSCH).
 10. The method of claim 1,wherein an uplink traffic channel is scheduled to be communicated in atime interval for the second EUTRA subframe, the method furthercomprising deciding to not transmit the uplink traffic channel so thatthe second EUTRA subframe carrying the second repeated instance in anuplink control channel is sent.
 11. The method of claim 1, furthercomprising: receiving, by the first wireless device, a parameter set bythe second wireless device to configure a number of repeated instancesof acknowledgment information to send by the first wireless device inresponse to information received from the second wireless device.
 12. Afirst wireless device comprising: an interface to communicate wirelesslyto a second wireless device; and a processor configured to: in responseto receipt of first information from the second wireless device, prepareto send repeated instances of acknowledgment information for the firstinformation; send a first of the repeated instances of theacknowledgment information in a first Evolved Universal TerrestrialRadio Access (EUTRA) subframe, and a second of the repeated instances ina second, successive EUTRA subframe; and send further acknowledgmentinformation in the second EUTRA subframe, wherein the furtheracknowledgment information is responsive to second information receivedfrom the second wireless device, wherein sending the second of therepeated instances of the acknowledgment information comprises using afirst information bit of the second EUTRA subframe, and wherein sendingthe further acknowledgment information comprises using a secondinformation bit of the second EUTRA subframe.
 13. The first wirelessdevice of claim 12, comprising a mobile station.
 14. The first wirelessdevice of claim 12, comprising a base station.
 15. The first wirelessdevice of claim 12, wherein the processor is configured to furtherreceive a parameter configuring a number of the repeated instances ofacknowledgment information, and wherein preparing to send the repeatedinstances of the acknowledgment information is according to the receivedparameter.
 16. The first wireless device of claim 15, wherein thereceived parameter specifies that the number is three or greater, andwherein the processor is configured to further send a third of therepeated instances in a third EUTRA subframe.
 17. The first wirelessdevice of claim 16, wherein receiving the first and second informationcomprises receiving the first and second information in respective firstand second traffic EUTRA subframes that are separated by at least oneEUTRA subframe.
 18. The first wireless device of claim 12, wherein usingthe first and second bits comprises using first and second ACK/NAK bits.19. At least one non-transitory, computer-readable storage mediumcontaining instructions that upon execution by a first wireless devicecause the first wireless device to: receive first information from asecond wireless device; send repeated instances of acknowledgmentinformation for the first information, wherein the repeated instances ofthe acknowledgment information are sent in consecutive subframes to thesecond wireless device; receive second information from the secondwireless device; and send further acknowledgment information for thesecond information, wherein the further acknowledgment information isincluded in one of the Evolved Universal Terrestrial Radio Access(EUTRA) subframes carrying one of the repeated instances of theacknowledgment information for the first information, wherein sendingthe further acknowledgment information for the second informationcomprises using a first information bit of the EUTRA subframe carryingone of the repeated instances, and wherein sending the furtheracknowledgment information comprises using a second information bit ofthe EUTRA subframe.
 20. The first wireless device of claim 18, furthercomprising modulating the first and second 2 ACK/NAK bits in an uplinkcontrol channel subframe.
 21. The first wireless device of claim 20,wherein using the first and second ACK/NAK bits comprises using thefirst and second ACK/NAK bits of uplink control information in aphysical uplink control channel (PUCCH) subframe.